The present invention relates to a remote meter reading apparatus for automatically reading utility meters from a central location.
Such systems are known in which a remote central meter reading unit feeds clock or interrogation pulses to a selected meter over a transmission line. In response, the meter feeds to the remote unit data signals corresponding to the utility meter reading. The utility may be electricity, water, gas or the like.
However, some means must be provided to synchronize the meter to the reading unit. One such expedient is to provide a clear circuit in the meter to determine the beginning of data transmission. This increases the cost of the meter by a considerable amount. Another expedient is to construct the meter to generate a start signal and an end signal preceeding and following the data signals respectively. This also adds to the cost and complexity of the meter and reading unit to an unacceptable extent.
It is also possible to construct the meter to generate a plurality of synchronization signals preceeding the data signals. However, it is difficult to distinguish the first synchronization signals from the final preceeding data signals in a binary data transmission system.
This problem may be overcome by providing the synchronization signals in the form of a code which does not correspond to any possible combination of data signals. However, this also increases the cost and complexity of the system to an unacceptable extent.